Lepidodendra -with the Sigillaria) of the Favidaria-tj-pe. On the other hand, as already stated under Sigillaria, the ribbed Sigillaria} may be related through Ormoxylon and Dadoxylon to the modern Conifers, and the Favularice may be related to the Cycads. This re- lationship may be expressed as follows : —
Cycadaceoe. Coniferoe.
Dadoxylon.
Favularia ? Palaeoxylon. Ormoxylon†.
Dictyoxylon.
Sigillaria.
Rhytidolepis. Calamodendron. Favularia ? Calamopitus. Clathraria. Bornia. Syringodendron. Calamites. Lepidophloios. Equisetaceoe. Lepidodendron *. Lycopodiaceoe.
I do not give this Table with any view to theories of derivation, but merely as an expression of probable affinities among these very curious and ancient types of vegetation.
I may add here a few words with reference to Sphenophyllum, a genus which some authors unite with Calamites. The verticillate, cuneate, veiny leaves of this plant, and its spikes of fructification have long been known ; and in 1865 I was enabled by a specimen in the collection of Sir W. E. Logan to determine the structure of its stem, which contains a slender axis of reticulato-scalariform vessels of the type of those in Tmesipteris‡. These plants obviously had no connexion with Calamites or Calamodendron, but constitute a peculiar synthetic type, presenting points of resemblance to Ferns and Marsiliaceae.
In conclusion, and with reference to my former papers on the " Structures in Coal," I would repeat the statement made in those papers, that the tissues of Sigillaria, as defined in this paper, and of Calamodendron enter more largely than any others into the composition of the mineral charcoal, and other parts retaining structure, of the coal of Nova Scotia ; and I have reason to believe that similar tissues are at least very abundant in the coal of this country.
Supplementary Note. — Owing to the delay in the publication of the above paper, it is necessary to add the following statements : —
(1) Prof. Williamson has described another type of Calamitean stem, which he regards as intermediate between his Calamopitus and Calamodendron §, but which has the reticulated or multiporous vessels of the former. To Prof. Williamson is due the credit of recognizing this structure for the first time in English specimens, though, as above
- Including Sagenaria.
† Dawson, MS. ‡ Quart. Journ. Geol. Society, May 1866. § Manchester Lit. and Phil. Soc, Proceedings, 1870.
